Fly ash entrapment wall



Dec. 8, 1964 E. 1.. DAMAN FLY ASH ENTRAPMENT WALL Filed July 19 1961 e sh'eets sheet 1 INVENTOR fR/VES? L. OAMA/v ATTORNEY Dec. 8,1964 E. L. DAMAN 3,160,144

7 FLY Asa ENTRAPMENT WALL Filed July 19, 1961' 6 Sheets-Sheet 2 l lll'lrlllplzlllll Til j INVENTOR [EA/57- Z..- 0AMA/V ATTORNEY E. L. DAMAN 3,160,144

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FLY ASH ENTRAPMENT WALL Filed July 19, 1961 s Sheets-Sheet s Ti: I

INVENTOR EPA/67 A. OAMA A/ ATTORNEY s8, E. L. DAMAN 3,150,144

FLY ASH ENTRAPMENT WALL Filed IhiLy 339., 31 ,961 6 Sheets-Sheet 6 INVENTOR EPA/5 4. 041*: N

ATTORNEY United States Patent O 3,160,144 FLY ASH ENTRAPMENT WALL Ernest 1L. Daman, Westfield; N.3.,' amignor to Foster Wheeler Corporation, New York, N315 a corporation of New York Filed .Iuly 19, 1%1, Ser- No. 125,245 4 lClaims. (Elfin-435) This invention relates to furnaces." It is a fly ash en trapment means especially suitable for thecombustion of slag forming fuels.

In furnaces, for use with slag forming fuels, it is generally considered desirable that the amount of fly ash carried by combustion gases from the combustion zone to the. convection zone be kept to a minimum. Furthermore, it is advantageous todispose of the ash in a fused state. Toward these ends, relatively cool surfaces are provided in the combustion. zone. The flame stream is directed onto the cool surfaces so that slag resulting from combustion will freeze thereon. Fuel. particles adhere to the slag. Oxygen in the combustion gases flowing overthe slag, scrubs the fuel to oxidize combustible materials therein. As the slag layer thickens, slagrernote from the surface melts forming a slag stream which migrates down the surface under gravity thereby eflecting the removal of non-combustibles in liquid form. v

. Relatively ash-free" combustion gases'are now obtained by means of cyclone furnaces wherein a high velocity is imparted to a mixture of fuel air and combustion gases. The. flame stream is directed to "sweep arelatively cool cylindrical surface whereon a slag stream develops. H

Inherenetly, cyclone furnaces have operating problems whichmust be lived with. Extremely high operating temperatures liberate many more substances from coal than are usually vaporized in' combustion; Precipitation of .some of these substances in the convection zone is particularly onerous. Also it is necessary to impart very high air velocities, at a significant expenditure in energy to retain the slag on the Walls of the cyclone. It is-in these disturbing consequences that the desire to minimize fly ash carry over and excessive air pressureis rooted.

e The present inventionavoids this difliculty'by a novel furnace arrangement. More'particular ly, a plurality of burners are disposed to directlflamestream including fuel escape into the convectionzone' can be'returned to the I target wall for entrapment in-the'rnoltenslag so that dry fly ash disposal maybe virtually eliminated. Addition ally, the plural burner arrangement affords uniform slagging characteristics over a wide range of furnace load.

These and other advantages will appear more fully from the detailed description viewed in conjunction with the accompanying drawings with the same number designation for analogous elements throughout the various views and wherein:

FIGURE 1 is an elevation view in vertical section of. a reheat boiler embodying this invention.

FIGURE 2 is a sectional view taken along line 22 of FIGURE 1 and showing the relationship of the zig-zag target wall to the burners.

FIGURE 2A is comparable to FIGURE 2 and shows 3,26%,344 Patented Dec. 8, 1964 "ice FIGURE 5 is a' sectional view on an enlarged scale 7 taken along line 55-5 of: FIGURE 4. p

FIGURE 6 is a vertical section of a'cylindrical boiler embodying another form of thisinvention.

FIGURE 7 is a sectional view taken along line 7-7 of FIGURE 6'. p I 1 In FIGURES 1 and 2, furnace housing 11 defines a rectangular combustion chamber. First compartment 12 and secondcompartment 14 are defined'in housing 11 by longitudinal target wall 16 and are communicated by passage means 17. Second compartment 14 is serially arranged relative to convection section 18 and flue 19 which provide means for removal of combustion gases from the chamber. I V p Burners communicate, with a source of pulverized fuel and a source of oxygen (neither of which are shown). Burners are divided into a firstportion 23 which direct their flame streams transversely into fifst compartment 12 and a second portion 24 which direct their flame streams transversely into second compartment 14.

. Fly Ash Entrapment" Means for fly ash entrapment are shown as target wall 16. Means" for'cooling target wall 16 are shown as tubes 26 fromwhich ceramic material 27 depends. The cooling means maintains the target wall below the freezing (fusion) temperature ofl'th'e' non-combustible fly ash material so that slag will'fr'eeze' on the wall.

*Undulations of target wall 16 provide troughsls on the first compartment side. which'alternat'es with troughs 29 on the second compartment side thereof. 'Each of the troughs 28, 29 are arranged to receive flame comprising a mixture of'fuel oxpgen and combustion gases from at least one of the burners 23, 24; The burners can be arranged to intercept the troughs either normally bisectingtroughs 23, '29as shown in FIGURE 2 .or obliquely relative target wall 16 as shown inFIGURE 2A. The flame stream courses around the'trough in sweeping relationshiprelative .targetwall 16 thereby depositing a coating of frozen slag31; Fuel'particles stick to the slag 31 andare scrubbed by oxygen which sweeps by in the flame.

- s As :thelayer of slag 31 builds up; slag remote from the target wall becomes hotter because of the insulating quality of the fly ash materialpreventing theflow of heat to tubes 26. When a sufficient coating 31 of slag has been established, the slagremote from target wall 16- melts and flows downward under gravity. Means for exhausting molten slag are shown as ports'32j. e I

p Rec ircylbiion of Dry Fly Ash V A Collection means which can-take the form of a dry .fly ash precipitator (not shown) are employed to recover Superheater Regulation Super-heater regulation means shown in FIGURE 1 comprises dampers 35 which are well-known in the art operatively connected to first group of burners 23 and Conduit means return the dry .fly

second group of the burners '24. By regulating the flow through first 23 and second 24 burners, respectively,'the rate of flow through passage means 17 may be determined. In this manner, the degree of efiectiveness of a superheater or reheater 33 may be controlled.

Tubes 26 forming target wall 16 also form division wall 34 and are opened to define screens 36 which serve as passage means 17. Of course, arrangements are possible wherein convection sections could be provided on both sides of the furnace housing in instances where greater superheater or reheater space is required.

The embodiment shown in FIGURES 4 and 5 has only a single compartment 12 and is fired from only-one side. Target Wall 16 is disposed closer to the burners than it would be in a conventional boiler. Above target wall 16, rear wall 37 slopes back to provide transition into conventional furnace cross-section above the ash separating zone.

As shown in FIGURES 6 and 7, this invention is also adaptable to cylindrical boilers. This feature would be of particular interest for supercharged designs since it would permit inclusion of the stress distribution advantages available with cylindrical shells.

It will be understood by those familiar with the furnace art that wide changes may be made in the details of con struction and the correlation of the various elements of this fly ash entrapment means without departing from the scope of the invention as defined by the claims.

What is claimed is:

1. In a furnace including a housing which defines a combustion chamber, means for exhausting combustion gases from the chamber; the combination comprising a burner having a longitudinal axis; sources of slag forming coal and oxygen communicating with the burner, the burner disposed to direct a burning slag forming coal stream into the chamber; a means for fly ash entrapment comprising a target Wall in the chamber; means for cooling the target wall below the freezing temperature of non-combustible material in said coal stream; the target wall describing an upright trough having converging side walls joined along the narrow portion of the trough and w grating down the trough and trapping coal particles from the stream of flame and coal for brushing engagement with oxygen in the stream; and means for exhausting molten slag from the trough.

2. In a furnace including a housing which defines a combustion chamber, means for exhausting combustion gases from the chamber; the combination comprising a course the upright walls of the trough in sweeping relationship therewith coating the trough with molten slag; means for cooling the target wall arranged to maintain the target wall below the fusion temperature of the slag causing an innermost layer of the slag to freeze, an outermostmolten layer migrating down the trough; the molten layer trapping coal particles from the stream of flame and coal for brushing engagement with oxygen in the stream; and means for exhausting molten slag from the trough.

3. In a furnace for the combustion of a slag forming coal having a substantial portion of non-combustible material, with the furnace including a housing which defines a combustion chamber, means for exhausting combustion gases from the chamber; the combination comprising a plurality of burners each having a longitudinal axis; sources of oxygen and slag forming coal communicating with each burner, each burner disposed to direct a burning slag forming coal stream into the chamber; a means for fly ash entrapment comprising a target ,wall disposed in the chamber; the target wall describing a plurality of undulations including upright troughs each having converging side walls joined along the narrow portion of the trough and an area in the wide portion of the trough substantially greater than the cross-sectional area of the burner streams; the troughs diverging towards the burners and being disposed in spaced relationship with the burners approximately perpendicular to the burner axes, in the paths of the streams of flame and coal from the burners; means for cooling the target wall below the freezing temperature of non-combustible material in said coal streams; at least two of the troughs each arranged for receiving a stream of flame and coal lit-om at least one of the burners causing the stream to approximately horizontally course the upright walls of that trough in sweeping relationship therewith coating the trough with molten slag, the molten slag migrating down the trough and trapping coal particles from the stream of flame and coal for brushing engagement with oxygen in the stream;

' and means for exhausting molten slag from the troughs.

burner having a longitudinal axis; sources of slag forming I ment comprising a target wall of aceramic material disposed in the chamber; the target wall describing an up- 4. The combination of claim 3 wherein said troughs have top and bottom walls defining ends for the troughs, the streams of flame and coal also coursing said top and bottom walls.

References Cited in the fileof this patent V UNITED STATES PATENTS 

1. IN A FURNACE INCLUDING A HOUSING WITH DEFINES A COMBUSTION CHAMBER, MEANS FOR EXHAUSTING COMBUSTION GASES FROM THE CHAMBER; THE COMBINATION COMPRISING A BURNER HAVING A LONGITUDINAL AXIS; SOURCES OF SLAG FORMING COAL AND OXYGEN COMMUNICATING WITH THE BURNER, THE BURNER DISPOSED TO DIRECT A BURNING SLAG FORMING COAL STREAM INTO THE CHAMBER; A MEANS FOR FLY ASH ENTRAPMENT COMPRISING A TARGET WALL IN THE CHAMBER; MEANS FOR COOLING THE TARGET WALL BELOW THE FREEZING TEMPERATURE OF NON-COMBUSTIBLE MATERIAL IN SAID COAL STREAM; THE TARGET WALL DESCRIBING AN UPRIGHT TROUGH HAVING CONVERGING SIDE WALLS JOINED ALONG THE NARROW PORTION OF THE TROUGH AND AN AREA IN THE WIDE PORTION OF THE TROUGH SUBSTANTIALLY GREATER THAN THE CROSS-SECTIONAL AREA OF SAID STREAM; THE TROUGH DIVERGING TOWARDS THE BURNER AND BEING DISPOSED IN SPACED RELATIONSHIP WITH THE BURNER APPROXIMATELY PERPENDICULAR TO THE BURNER AXIS, IN THE PATH OF THE STREAM OF FLAME AND COAL FROM THE BURNER, CAUSING THE STREAM TO APPROXIMATELY HORIZONTALLY COURSE THE UPRIGHT WALLS OF THE TROUGH IN SWEEPING RELATIONSHIP THEREWITH COATING THE TROUGH WITH MOLTEN SLAG, THE MOLTEN SLAG MIGRATING DOWN THE TROUGH AND TRAPPING COAL PARTICLES FROM THE STREAM OF FLAME AND COAL FOR BRUSHING ENGAGEMENT WITH OXYGEN IN THE STREAM; AND MEANS FOR EXHAUSTING MOLTEN SLAG FROM THE TROUGH. 